Vocabulary
首をひねる
くびをひねる
to cock one's head in puzzlement; to tilt one's head in contemplation; to wrack one's brain; to think hard
expression
verb
Example sentences
私（わたし）はその数学（すうがく）の難問（なんもん）に首（くび）をひねった。
I puzzled over the difficult math problem.